This invention features assays and devices for the detection of analytes, and their use in the treatment and diagnosis of disease.
Magnetic sensors have been designed to detect molecular interactions in a variety of media, including biofluids, food products, and soil samples, among other media. Upon target binding, these sensors cause changes in properties of neighboring water molecules (or any solvent molecule with free hydrogens) of a sample, which can be detected by magnetic resonance (NMR/MRI) techniques. Thus, by using these sensors in a liquid sample, it is possible to detect the presence, and potentially quantify the amount, of an analyte at very low concentration. For example, small molecules, DNA, RNA, proteins, carbohydrates, organisms, metabolites, and pathogens (e.g., viruses) can be detected using magnetic sensors.
In general, magnetic sensors are magnetic particles that bind or otherwise link to their intended molecular target to form clusters (aggregates). It is believed that when magnetic particles assemble into clusters and the effective cross sectional area becomes larger (and the cluster number density is smaller), the interactions with the water or other solvent molecules are altered, leading to a change in the measured relaxation rates (e.g., T2, T1, T2*), susceptibility, frequency of precession, among other physical changes. Additionally, cluster formation can be designed to be reversible (e.g., by temperature shift, chemical cleavage, pH shift, etc.) so that “forward” or “reverse” (competitive and inhibition) assays can be developed for detection of specific analytes. Forward (clustering) and reverse (declustering) types of assays can be used to detect a wide variety of biologically relevant materials. The MRS (magnetic resonance switch) phenomenon was previously described (see U.S. Patent Publication No. 20090029392).
Many diagnostic assays require sensitivity in the picomolar or subpicomolar range. In such assays an equally low concentration of paramagnetic particles is employed. As a result, the binding events leading to cluster formation can become a rate-limiting step in the completion of the assay as the collision frequency of antigens, paramagnetic particles, and partially formed clusters is low in this concentration range (see Baudry et al., Proc Natl Acad Sci USA, 103:16076 (2006)). The current detection of infectious agents, nucleic acids, small molecules, biowarfare agents and organisms, and molecular targets (biomarkers) or the combination of molecular and immunoassay targets usually requires up-front sample preparation, time to analyze the sample, and single tests for each of the individual analytes. There is a need for a rapid, commercially-realizable NMR-based analyte detection device suitable for use with magnetic nanosensors having four unique features and qualities: 1) little to no sample preparation, 2) multiplex detection across multiple molecular types, 3) rapid acquisition of diagnostic information, and 4) accurate information for point-of-care clinical decision making.